This invention pertains to a landfill method particularly useful for making synthetic aggregate and to the aggregate made thereby.
The manufacture of synthetic aggregate from hardened lime fly ash compositions, including in some cases flue gas desulfurization sludge solids, has previously been proposed. See, for example, U.S. Pat. No. 3,785,840 (of common assignment and partial common inventorship herewith). Generally, the methods proposed have involved forming aggregate shaped particles and curing them. These products have generally been unsatisfactory as synthetic aggregates for various reasons; most notably, usually poor abrasion resistance. Many efforts have also been made to improve the reactivity of lime-fly ash or lime-fly ash-sludge compositions. See, for example, U.S. Pat. No. 4,613,374, a sole invention of one of the co-inventors herein (and of common assignment herewith). The possible criticality of compression or pressure in the forming of such mixes to make the products has been noted in other contexts. See, for example, U.S. Pat. No. 4,377,414--Buschmann et al. More specific efforts to produce a synthetic aggregate from lime and fly ash, together in some cases with other waste materials, are reflected in the commercial products known as Agglite (a combination of Portland cement and fly ash) and Aardelite (lime and fly ash). References specifically describing these products include:
______________________________________ Agglite: U.S. Pat. No. 4,624,711 U.S. Pat. No. 4,741,782 ______________________________________
Fly Ash Lightweight Aggregate: The Agglite Process--Styron, Proceedings, Eighth International Ash Utilization Symposium (1987) pp. 58-1 to 58-12.
The Aggregate of the Future is Here Today--Courts, Proceedings, Ninth International Ash Utilization Symposium (1991) pp. 21-1 to 21-10.
______________________________________ Aardelite: U.S. Pat. No. 4,394,176 U.S. Pat. No. 4,419,312 U.S. Pat. No. 4,490,178 ______________________________________
Manufacturing Use of Artificial Aggregates from Fly Ash Produced According to the Dutch Cold Bond "Aardelite" Process--Boas and Spanjer, Proceedings British Ash Symposium (1984)
Lightweight Aggregate Production and Use in Florida--Hay and Dunstan, Proceedings, Ninth International Ash Utilization Symposium (1991) pp. 22-1 to 22-10.
Artificial Gravel as a Gravel Substitute in Asphaltic Concrete--Mulder and Houtepen, Proceedings, Ninth International Ash Utilization Symposium (1991) pp 23-1 to 23-11
Testing of Manufactured Gravel for Products Specification in Israel (1988--1989)--Boas, Proceedings, Ninth International Ash Utilization Symposium (1991) pp. 24-1 to 24-13.
Additional references reflecting other recent attempts to make synthetic aggregate also include:
Templite Catalyst--A New Construction Material--Temple and Styron, from (Source unknown), pp 232 to 239
Fly Ash Lightweight Aggregate: A New Process--Styron, Proceedings, Seventh International Ash Utilization Symposium and Exposition, Volume II, (1985) pp 835 to 844.
Synthetic Gravel from Dry Fly Gas Desulfurization End-Products--Donnelly, Jons and Webster, Proceedings, The Challenge of Change--Sixth International Ash Utilization Symposium (1982) pp. 187 to 207.
Utilization of Advanced SO.sub.2 Control By-Products: Laboratory Test Results--Manz, Collings, Perri and Golden, Proceedings, Eighth International Ash Utilization Symposium, Volume 1 (1987) pp. 8-1 to 8-19.
Notwithstanding these prior efforts, there remains a need for a synthetic aggregate product, preferably a light-weight product, suitable for use in ordinary construction and economically producible from waste materials such as fly ash, and most particularly also including flue gas desulfurization sludge.